It is not overly difficult. The hardest part will be working with the flex cables that lay ontop of the hard drive. If you tear one of these cables you will have to dig up a new one.

Take out all the back and side screws and put them in a pile, should be 10 or so. Remove the ram bay door, remove the screws on the front wall under the battery, remove the tork screws under the ram door.

Then you can pry up the top case, start towards the screen and arch it back. Once off you can remove the 4 tork screws that hold the HD in place.

If you are uncomfortable with it try to dig you a local apple certified technician. Someone like myself would charge $50 or so dollars to toss one in, if you bring it to a brick and mortar location they may charge as much as $100. If you happen to know any techs a six pack of beer works just as well.

If you hit any trouble feel free to contact me I can walk you through the process.

I took my MBP to a local Mac repair shop and they charged me $60 (which I think was their minimum labor charge). Seeing as how I didn't have the tools, didn't want to void my warrant, and after a friend of mine spent two hours doing it himself and told me to just pay the $60, I figured that was the easier route.

So I would try calling around first if you have any local Mac repair guys in your area and see how much they would charge for a simple hard drive swap.